1. Field of the Invention
This invention relates to a back light for a liquid crystal display device, and more particularly to an apparatus for fixing an optical film to the outer frame of the back light.
2. Description of the Related Art
Basically, a liquid crystal display device that has been widely used for a display device such as a notebook computer or a portable television, etc., includes an upper plate and a lower plate, a liquid crystal panel consisting of a liquid crystal layer provided between the upper plate and the lower plate, and a back light installed at the lower surface of the lower plate to provide a uniform light source.
Generally, as shown in FIG. 1, the back light of the liquid crystal display includes an outer frame (or main supporter) 1, a light-conductive plate 2 installed within the outer frame 1, a reflecting film 3 provided in opposition to the lower surface of the light-conductive plate 2; and a lower diffusion film 4, a lower prism film 5, an upper prism film 6, and an upper diffusion film 7 that are disposed on the upper surface of the light-conductive plate 2. The light-conductive plate 2 converts light generated from a light source installed at one side of the outer frame 1 into light emerging from an upper face of the light-conductive plate 2. The reflecting film 3 reflects incident light from the lower surface of the light-conductive plate 2, back toward the light-conductive plate 2. The lower diffusion film 4 diffuses light passing through the upper surface of the light-conductive plate 2 into the entire surface of the back light. The lower prism film 5 and the upper prism film 6 converge light received from the lower diffusion film 4 into a desired direction by their polarization characteristics. The upper diffusion film 7 diffuses light passing through the upper prism film 6, again, and protects the upper prism film 6. Pads 8 are attached to the edges of the upper surface of the upper diffusion film 7. The pads 8 are responsible for supporting a liquid crystal panel(not shown).
The four optical films 4, 5, 6 and 7 are adhered to double-face tapes 9 to be fixed to the outer frame 1. The upper diffusion film 7 is fixed onto the upper surfaces of the projections formed within the outer frame 1 with the aid of the double-face tapes 9, whereas the remaining three optical films 4, 5, and 6 are fixed to the side wall surfaces of the projections of the outer frame 1 with the aid of the double-face tapes 9.
The method of fixing the four optical films 4, 5, 6 and 7 using the double-face tape 9 in this manner causes the following problems. First, each of the optical films 4, 5, 6 and 7 requires a separate process of adhering the double-face tape 9 and a separate assembly process for fixing each of the optical films 4, 5, 6 and 7 to the outer frame. So the number of processes is the same as the number of optical films. For this reason, the assembly time of the back light is increased, and the defect rate is also increased to that extent. For instance, in the case of the back light as shown in FIG. 1, since four optical films 4, 5, 6 and 7 are provided, a process of adhering the double-face tape 9 to the optical films 4, 5, 6 and 7 is required to be performed four times, and an assembly process of fixing the optical films 4, 5, 6 and 7 also is required to be performed four times. Second, since a portion of the optical films 4, 5, 6 and 7 fixed with the aid of the double-face tape 9 and the pad 8 has a different expansion degree from the remaining unfixed portion thereof at a high temperature, wrinkles are generated at the optical films 4, 5, 6 and 7 at a high temperature.
Accordingly, it is an object of the present invention to provide a back light for a liquid crystal display device that is adapted to provide a reduce assembly time as well as preventing wrinkles from being generated at optical films at a high temperature.
In order to achieve these and other objects of the invention, a back light of a liquid crystal display device according to one aspect of the present invention includes a protrusion protruded from a frame rim of an outer frame; a film extension extended from one side edge of an optical film to be put on the surface of the frame rim near the protrusion; and a clip provided with a hole for inserting the protrusion to be mounted onto the frame rim in such a state that the protrusion has been inserted into the hole, thereby fixing the film extension of the optical film onto the frame rim.